Audio watermarking is the process of embedding in an inaudible way additional information into an audio signal. The embedding is performed by changing the audio signal, for example by adding pseudo-random noise or echoes. To make the embedding in-audible, the strength of the embedding is controlled by a psycho-acoustic analysis of the audio signal. WO 2011/141292 A1 describes watermark detection in the presence of echoes, reverberation and/or noise in an audio signal, e.g. loudspeaker sound received by a microphone. These echoes are resulting in multiple peaks within a correlation result value sequence of length N with a watermark symbol (i.e. a reference signal), and are used for improving the watermark detection reliability. Basic steps of that statistical detector are:                Find peak values v=(v1, v2, . . . , vnp) in the correlation result sequence for each candidate watermark symbol, where v1≧ . . . ≧vnp and np is the number of correlation result peak values taken into consideration;        Recursively calculate the false positive probability P(k), k=1, . . . , np, of the candidate watermark symbol being embedded;        Select the candidate watermark symbol resulting in the lowest P(k) value.        
P(k) is the probability of falsely accepting the candidate watermark symbol. It describes the probability of k or more correlation result values from a non-watermarked signal section being greater than or equal to the actual k peak values under consideration.
That statistical detector solves the following problems:                a) How to recursively evaluate the probability P(k), where the number k of considered peak values can be increased gradually.        b) How to minimise the computational complexity by re-using already performed calculations.        
That statistical detector uses several correlation result peaks in order to improve the detection performance. Especially this improvement is advantageous if the watermarked tracks are transmitted over an acoustic path resulting in multipath detection due to echoes. The np peaks v1≧ . . . ≧vnp used for calculating P(k) are taken from the whole correlation result value sequence of length N.